Stabilization of unsaturated ketones



Patented Sept. 4, 1 951 Hans Dannenberg, lldcrkeley Calif assignor tShell Development Company, San Francisco,

Califl, a corporation of Delaware No Drawing. Application May 25, 194 8,

* SerialNo. 29,137

This invention relates to the stabilization of unsaturated ketones andto the stable compositions of matter produced thereby. It relates moreparticularly to the stabilization of normally liquid unsaturated ketoneshaving an unsaturated group of at least three carbon atoms attached tothe carbonyl group, this group comprising an unsaturated tertiary carbonatom. A particular aspect of the invention relates to the rendering ofthese unsaturated ketones color stable under conditions normallyencountered during their transportation and/or storage.

Unsaturated lretones find application in many industrial processes. Intheir utilization it. is generally necessary that they meet exactingspecifications, one of which is that they be substantially free ofcoloring matter. These unsaturated ketones, however, are generally proneto undergo deterioration, resulting in the formation therein of colorimparting contaminants.

The presence of the color imparting impurities generally renders theunsaturated ketones unsuitable for many of the purposes for which theyare intended. Without in any Way intending to limit the scope of thepresentinvention by any theories advanced herein to set forth moreclearly the nature of the invention, it is believed that the colorimparting impurities may well be due to the formation of oxidationproducts of the unsaturated ketones comprising diketones. It has beenfound that deterioration and formation of the color imparting impuritiesis favored by the conditions generally encountered in the storage andtransportation of the materials involving their prolonged contact withmetal-containing, and particularly ferruginous, materials. A Water-whiteunsaturated ketone, such as, for example, mesityl oxide, is often foundto become discolored under normal conditions encountered in storageand/or transportation at such a rapid rate that its color is generallyof medium yellow to amber after a period of only about fourteen days. Asa result of such contamination of the unsaturated ketones it hasgenerally been necessary to subject the material to a purificationoperation to render it suitable for many of its more important uses.Such purification often entails costly operations due to the difficultyencountered in attempting the separation of the color-impartingcontaminants by generally available means. The various inhibitors whichhave heretofore been proposed to suppress the deterioration ofunsaturated ketones, while in some instances fairly effective, are ingeneral unsuited either because of the very short period of theireffectiveness, their relative ineffectiveness under conditions generallyencountered in storage and shipment, especially when in contact withmetalcontaining surfaces, or because of the .dif:

2 ficulties encountered in separating the inhibitor, when necessary,after, ithas. servedits; ,-.purpose. "As, disclosed in co-pendingapplication Serial No.582,5:89,'fi1ed March 13;; 1945;of whichi thepresent application" is a continuation-impart, andwhich issued as PatentNo; 2,44l,0 06 on,.J une 22,1948; it has now been found ,thatthedeterioration of unsaturated ketones particularlyayvlth respect todiscoloration may -be suppressed to at least a substantial degree under:QOlflditlQIiS generally'encountered in shipment and storage. evenin thepresence of metal-containing sun faces by incorporating therein arelatively, small amountof asecondary amine. The present invention isadapted to the stabilization, particularly with respect to color, of allunsaturated ketones having anunsaturated group of at least three, carbonatomsgsaid-pnsaturated group having an unsaturated "tertiary carbonatom. Examples of this'particular-group of unsaturated 'ketonescomprise: "methyl :isopropenyl ketone, ethylisopropenyl ketone, methyli'sobutenyl" ketone, p'ropyl 3 isopropenyl: ketone,cy'clopentylisopropenyl ketone, allyl isopropenyl lieton'e,di-isopropehyl ketone, Z-ethyI-biitene-I one-3',2-pr0pyl-butene-1-ohe-31Z-ethyl-penteriehone-'3,- 2methyl-pentene-1one-4;'="2-metnylhexene-2-one-"4, 3-methyl pentene-2-one4; 2- nietl'iyl-pe'nte'n'e-z-onel,3 etliyl p'enten 2-one- 4-;"2-ethyl-p'er'itene-2 one l; isophdrone; and" the like asfw'ell astheir'homologues, analogues anu suitable substitution products thereof.1 i lhe'" irivention is, however} particularly applicable "to thestabilization, especiallywith respect to color, of alpha-betaunsaturated sewn-es ates unsaturateid'ftertiary carson attm m the betaposition 'll 'e following are "repiesentative unfsaturated ketones ofthis preferred group -to whichthe invention is partic T iiies'ityloxidegz -'f'rnethyl ixe Z m'ethyl -hepte'ne 12 ne; 5 hexane? 2 i one A4, 2 ethyl pent oiie -14, 3 methyl 'hexenf :3 ethyl hexene- 3 one 5, 2,2 heiien'e one 5,215 dimethyl h 2',5"-dne-4 and thelik'e, assures the's, analogues and suitable substitution p itsj therof;" lthoiigh theinhibitors of the invention are applied [Witlrparticular"advantage t "tbiliz'anor'l of the abcvegqefinde ou saturated ket'ones, the "avenuescomp sfe broadest scopefthestabilization of a liquid unsaturated ketone.other unsaturated lgetoine's comprlse dfw scopeof the invention arepetitesean A ene- -on r r n r i -fi reai 9 55 5-methy1 hexene-1-one-4, 5-methyl hexene Z- ewlr z-met yb exen -,0ne: hex dien-l- 3 one-4, and thelike as well as their homologues, analogues and suitable substitutionproducts.

The stabilizing materials incorporated in the unsaturated ketones to bestabilized in accordance with the invention comprise, in their broadestscope the dihetero-azines in which'a hydrogen atom is attached to anuclear nitrogen atom in the diheteroatomic azine ring. The heterocycliccompounds known collectively as the dihetero-azines consist of theheterocyclic compounds having a six-membered diheteroatomic ring inwhich one of the heteroatoms is nitrogen and the second heteroatom isnitrogen, oxygen or sulfur. The dihetero-azines consist of the diazines,oxazines and thiazines. The two heteroatoms may be .positionedin theortho, meta or para positions of the dihetero-azine ring.

The suitable dihetero-azines employed in the present invention are those'in which a nuclear nitrogen atom of the dihetero-azine ring isconnected to a hydrogen atom. The dihetero-azine compounds comprisedwithin the scope of the invention include those in which one or morecarbon atoms of the dihetero-azine ring, as well as the heteroatom otherthan the nitrogen atom contained in the nuclear amino group, aredirectly connected to substituent groups uch as, for example, alkyl,aryl, alkyl-aryl, aryl-alkyl, or other substituent groups. When thestructure of the diheteroazine is of non-aromatic character, this isgenerally expressed by reference thereto as a hydroazlne. Similarly thediazines, oxazines and thiazine of non-aromatic structure are designatedas hydrodiazines, hydrooxazines and hydrothiazines, respectively.

Illustrative .of the dihetero-azines having a hydrogen atom attached toa nitrogen atom in the dihetero-azine ring which as a class have beenfound peculiarly effective in their ability to stabilize the normallyliquid unsaturated ketones are the following: the hydro-1,2-diazines(hydro-pyridazines) such as, 3-phenyl-hexahydro-l,2 -diazine, 3.-methyl6 isopropyl l,4,5,6- tetrahydro 1,2 diazine, l phenyl-3-methyl-6-isopropyl 1,4,5,6-tetrahydro-1,2-diazine,3,6-dimethyl-hexahydro-1,2-diazine; the hydro-1,3-diazine(hydro-pyrimidines) such as hexahydro- 1,3-diazine,2,4,4,6-tetramethylhexahydro-l,3-diazine, 2-phenyl-4,6-dimethylhydro-1,3diazine, 2,4,6-trimethyl 1,4,5,6 tetrahydro-l,3-diazine,2,4-dimethyl-B-amine-hydro-1,3-diazine; the hydro-1,4-diazines(hydropyrazines), such as hexahydro-l,4-diazine (piperazine) 2-phenylhexahydro-1,4 diazine, l,4-dihydro-l,4-diazine, 2,5-dimethyl-tetrahydro-IA-diazine; the hydro-1,2- oxazines such as,2,3,5,6-tetr ahydro-1,2-oxazine (oxazidine); the hydro-1,3-oxazines suchas, 2- phenyl-4,4,6 trimethyl tetrahydro-l,3-oxazine,4,4,6-trimethyl-tetrahydro-1,3-oxazine,G-methyl-4-isobutyl-tetrahydro-1,3-oxazine, 2-phenyl-5,6-dihydro-L3-oxazine,2-phenyl-4,4,6-trimethyl-5,6-dihydro-1,3-oxazine; the hydro-1,4-oxazinessuch as, tetrahydro-lA-uxazine (morpholine),2-phenyl-4,4,6-trimethyl-5,6-dihydrol,4 oxazine; the hydrothiazines suchas, 2,6-dimethyl tetrahydro-1,4-thiazine (2,6-dimethylthiamorpholine)tetrahydro-lA-thiazine' (thiamorpholine), lA-thiazine,2-phenyl-4,4,6-trimethyl-3,5,6 trihydro-l,3-thiazine, benzodihydrothiothiazine, their homologues, analogues and suitable substitutionproducts.

In contrast to this behavior of the above secondary amines; the primaryand tertiary amines are generally not only ineffective as stabilizersbut their incorporation into the unsaturated 4 ketones often results inan acceleration of discoloration. Of the above secondary amines thesaturated dihetero-azines have been found to be outstanding in theirability to stabilize the unsaturated ketones, particularly with respectto color. Of the suitable saturated dihetero-azines,

the alkyl substituted saturated dihetero-azines are preferred.Particularly effective are tetrahydro-L l-oxazine and its alkylsubstitution products especially its polymethyl substitution products asexemplified by 2,4, l,6-tetramethyltetrahydrooxazine.

A particular advantage of the secondary amines as stabilizers for theunsaturated ketones in accordance with the invention resides in theireffectiveness in the presence of metal-containing surfaces. Thus, it hasbeen found that substantial improvement with respect to color stabilityof the unsaturated ketones over prolonged periods of time, even in thepresence of ferruginous materials, is obtained by the incorporationtherein 01 the above heterocyclic secondary amines. JIhus, whereas asubstantially colorless unsaturated ketone, such as, for example,mesityl oxide, will turn yellow to amber in as short a period asfourteen days, the incorporation therein of a secondary amine of theabove-defined class of diheterocyclic secondary amines, such as, forexample, tetrahydro-l,4-oxazine (morpholine) will render itsubstantially color stable in the presence of iron over periodsexceeding about one hundred days.

The quantity of the heterocyclic secondary amine added to theunsaturated ketone to be stabi ize may vary within the scope of theinvention. The amount required to attain the desired degree of colorstability will vary not only in accordance with the particularunsaturated ketone stabilized but with the particular secondary amineemployed. In general, it has been found that the addition of theheterocyclic secondary amine to the unsaturated ketone in an amountranging from about 0.01% to about 3%, and preferably from 0.1% to about1% by weight has been found satisfactory. Higher or lower concentrationsof the secondary amine may however be resorted to Within the scope ofthe invention. The secondary amine may be added to the unsaturatedketone as such or it may be added to only a portion of the unsaturatedketone and the resulting mixture or solution then added to the remainingketone in an amount sufficient to attain the desired concentration ofthe stabilizer therein.

The unsaturated ketone may be recovered from the color stablecomposition of matter, comprising the unsaturated ketone and inhibitingamount of secondary amine, by any suitable means. Thus the secondaryamine may generally be readily removed by one or more of such stepscomprising, for example, distillation, fractionation, adsorption.solvent extraction, etc.

The following examples are illustrative of the invention:

Eight samples, each consisting of cc. of mesityl oxide in a glassstoppered, cc. bottle were prepared. To each of seven of the samplesthere was added an amine in an amount equal to one millimole of therespective amine. To all the samples containing the added amine, and tothe sample containing no added amine, there was added a rusty three-inchnail as a source of iron. To further simulate normal storage and trans-'5 portation conditions all of the samples were stored in the dark atroom temperature for fourteen days. At intervals the samples werecarefully examined and their color determined. Color of the sample wasobtained and recorded by comparison with standard liquids consisting ofaqueous solutions of potassium bichromate which were contained insimilar bottles. The following color scale, based upon the color of theaqueous solutionsof potassium bichromate was used:

Color scale Very faint yellow, corresponding to 0.5 mg.

K2CI2O7 per 100 cc.

. Faint yellow, corresponding to 1 mg. K2CI'2O7 per 100 cc.

. Very slight yellow, corresponding to 1.5

K2CI'2O7 per 100 cc.

. Slight yellow, corresponding to 2.5 mg. K2Cr2O7 per 100 cc.

. Medium yellow, corresponding to 5 mg. mono per 100 cc.

. Dark yellow 1 Light amber 1 Dark amber 1 These colors were notdetermined quantitatively.

The particular amine added to each sample, and the color determinationobtained at each examination during the storage period, are indicated inthe following table A:

Table A assayed ple, and the color determination obtained at eachexamination during the storage period, arcindicated in the followingTable B:

Four samples, each consisting of 1001 cc. of mesityl oxide in a glassstoppered, 125 cc. bottle 0 were prepared. The mes-ityl oxide employedwas obtained from a different source than that used in Examples I andII. To each of two of the samples there was added an amine in an amountequal to one millimole of the respective amine.

amine, there was added a rusty three-inch nail as a source of iron. Tofurther simulate normal storage and transportation conditions, all ofthe samples were stored in the dark at room tem erature for 92 days. Atfrequent intervals the sam-- ples were carefully examined and theircolor-dee Storage in days"...

Sfilll Stabilizer added olor readings Hexahydro-1,4-diazine2,6-Dimethyltetra-hydro-1,4,thiazine z-Phenyl 4,4,6trimethyltetrahydrooxazine. 2,4,4,6-1etramethyltetrahydrooxezine. 2,4,4,6-Tetramethylhexahydro-l,3-diazine. Diiso r0 ylarnine Tetra yro-lA-oxazine (morph None and: cumwcezo EXAMPLE II Four samples, eachconsisting of 100 cc. of mesityl oxide in a glass stoppered, 125 cc.bottle were prepared. To each of the samples there was termined. Thecolor scale given in Example I 50 was used. The particular amine addedto each sample, and the color determination obtained at each examinationduring the storage period; are indicated in the following Table C:

Table C stdmgein days 1 3 6 9 12 1e 31 e1 e2 Sample Stabilizer added F9Color reading No. Present 1 TetfiaPydro-lA-oxezine (mor- Yes..- 1 1 1.25 1.25 1.5 1. 75 2 2.75 2.751

p 0 e V 2; Mono-ethanolamine Yes..- 1 5 5 5 6 6 6 8 7 3 None Yes--. 1.52 3.5 4.25 4.5 5 e 7.5 s

4 None No 1.5 2.5 4 5 5 '6 '6 o 6 I claim as my invention:

1. An unsaturated ketone stabilized against color change under normalconditions encountered in storage and transportation consistingessentially of a normally liquid olefinically unsaturated ketonecontaining a diheteroazine containing a six-membered dihetero-atomicring in.

which both heteroatoms are nitrogen and a hydrogen atom is attached to anuclear nitrogen To the two samples containing the added amine,. and toone of the samples containing no added.

atom of the diheteroatomic ring in an amount sufficient to inhibitdiscoloration of said un saturated ketone. r

2. An unsaturated ketone stabilized against color change under normalconditions encountered in storage and transportation consistingessentially of a normally liquid oleflnically unsatue rated ketonecontaining from about 0.01%. to about 3% by weight of a dihetero-azinecontaining a six-membered dihetero-atomic ring in which both heteroatomsare nitrogen and in which a hydrogen atom is attached to a nuclearnitrogen atom of the diheteroatomic ring.

3. An unsaturated ketone stabilized against color change under normalconditions encountered in storage and transportation consistingessentially oi normally liquid unsaturated ketone having an unsaturatedgroup of at least three carbon atoms attached to the carbonyl group,said unsaturated group having an unsaturated tertiary carbon atom,containing from about 0.01% to about 3% by weight of a dihetero-azinecontaining a siX-membered dihetero-atomic ring in which both heteroatomsare nitrogen and in which a hydrogen atom is attached to a nuclearnitrogen atom of the diheteroatomic ring.

4. An unsaturated ketone stabilized against color change under normalconditions encountered in storage and transportation consistingessentially of a normally liquid alpha-beta unsaturated ketone having anunsaturated tertiary carbon atom in the beta position containing fromabout 0.01% to about 3 by weight of a diheteroazine containing asix-membered dihetero-atomic ring in which both heteroatoms are nitrogenand in which a hydrogen atom is attached to a nuclear nitrogen atom ofthe diheteroatomic ring.

5. Mesityl oxide stabilized against color change under normal conditionsencountered in storage and transportation consisting of mesityl oxidecontaining from about 0.01% to about 3%"by weight of a dihetero-azinecontaining a sixmembered dihetero-atomic ring in which both heteroatomsare nitrogen and in which a hydrogen atom is attached to a nuclearnitrogen atom of the diheteroatomic ring.

6. An unsaturated ketone stabilized against color change under normalconditions encoun 9. An unsaturated ketone stabilized against colorchange under normal conditions encountered in storage and transportationconsisting of tered in storage and transportation consisting andtransportation consisting of 'mesityl oxide containing from about 0.01%to about 3% by Weight of hexahydro-1,4-diazine.

8. Mesityl oxide stabilized against color change under normal conditionsencountered in'storage and transportation consisting of mesityl oxidecontaining from about 0.01% to about 3% by.

weight of 2,4,4,6-tetramethylhexahydrodiazine.

an alpha,beta-unsaturated ketone having an unsaturated tertiary carbonatom in the beta position containing from about 0.01 to about 3% byweight of hexahydro-lA-diazine.

10. An unsaturated ketone stabilized against color change under normalconditions encountered in storage and transportation consisting of analpha,beta-unsaturated ketone having an unsaturated tertiary carbon atomin the beta posi' tion containing from about 0.01% to about 3% by weightof 2,4,4,6-tetramethylhexahydro-1,3- diazine. 7 V e 11.- The method ofinhibiting the discoloration of mesityl'oxide under normal conditionsencountered in storage and transportation which consists of adding tosaid mesityl oxide from about 0.01% to about 3% by weight of adihetero-azine containing a six mcmbered diheteroatomic ring in whichboth heteroatoms are nitrogen and in which a hydrogen atom is attachedto a nuclear nitrogen atom in the diheteroatomic ring.

12. The method of inhibiting the discoloration of an unsaturated ketoneconsisting essentially of a normally liquid alpl1a,beta-unsaturatedketone having an unsaturated tertiary carbon atom in the beta positionunder normal conditions encountered in storage and transportation whichconsists of adding tosaid ketone from about 0.01% to about 3% by Weightof a dihetero-azine containing a six-membered diheteroatomic ring inwhich both heteroatoms are nitrogen and in which a hydrogen atom isattached to a nuclear nitrogen atom in the diheteroatornic ring.

"13. enerates: inhibiting the discoloration of a normally liquidolefinically unsaturated ke-' tone under normal conditions encounteredin storage and transportation which consists of adding to said ketone adihetero-azine containing a six-meinbered diheteroatomic ring in whichboth heteroatoms are nitrogen and in which a hydrogen atom is attachedto a nuclear nitrogen atom in'the diheteroatomic ring in an amountsufficient to inhibit discoloration of said unsaturated l'lAN SDANNEN'Bl-IERGI REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 1,766,760 Morton June 24, 19302,001,584 Reed May 14, 1935 2,071,064 Downing et, a1 Feb. 16, 19372,087,597 Gutzeit July 20, 1937 2,121,010 Britten et a1 June 21, 1938Howl; Feb. 25, 1941 2,294,286 Dannenberg et al. Aug. 25, 1942 2,458,780Howland Jan. 11, 1949 Lincoln etal July 19, 1949

1. AN UNSATURATED KETONE STABILIZED AGAINST COLOR CHANGE UNDER NORMALCONDITIONS ENCOUNTERED IN STORAGE AND TRANSPORTATION CONSISTINGESSENTIALLY OF A NORMALLY LIQUID OLEFINICALLY UNSATURATED KETONECONTAINING A DIHETEROAZINE CONTAINING A SIX-MEMBERED DIHETERO-ATOMICRING IN WHICH BOTH HETEROATOMS ARE NITROGEN AND A HYDROGEN ATOM ISATTACHED TO A NUCLEAR NITROGEN ATOM OF THE DIHETEROATOMIC RING IN ANAMOUNT SUFFICIENT TO INHIBIT DISCOLORATION OF SAID UNSATURATED KETONE.